Multi-pollutants impact on modern cement built heritage

It is well known that the deposition of gaseous pollutants and aerosols plays a major role in causing the deterioration of monuments and built cultural heritage in European cities. Despite of many studies dedicated to the environmental damage of cultural heritage, in case of cement mortars, commonly used in the 20th century architecture, the deterioration due to air multipollutants impact, especially the formation of black crusts, is still not well explored making this issue a challenging area of research. This work centers on cement mortars – environment interactions, focusing on the diagnosis of the damage on the modern built heritage due to air multi-pollutants. For this purpose three sites, exposed to different urban areas in Europe, were selected for sampling and subsequent laboratory analyses: Centennial Hall, Wroclaw (Poland), Chiesa dell'Autostrada del Sole, Florence (Italy), Casa Galleria Vichi, Florence (Italy). The sampling sessions were performed taking into account the height from the ground level and protection from rain run off (sheltered, partly sheltered and exposed areas). The complete characterization of collected damage layer and underlying materials was performed using a range of analytical techniques: optical and scanning electron microscopy, X ray diffractometry, differential and gravimetric thermal analysis, ion chromatography, flash combustion/gas chromatographic analysis, inductively coupled plasma-optical emission spectrometer. The data were elaborated using statistical methods (i.e. principal components analyses) and enrichment factor for cement mortars was calculated for the first time. The results obtained from the experimental activity performed on the damage layers indicate that gypsum, due to the deposition of atmospheric sulphur compounds, is the main damage product at surfaces sheltered from rain run-off at Centennial Hall and Casa Galleria Vichi. By contrast, gypsum has not been identified in the samples collected at Chiesa dell'Autostrada del Sole. This is connected to the restoration works, particularly surface cleaning, regularly performed for the maintenance of the building. Moreover, the results obtained demonstrated the correlation between the location of the building and the composition of the damage layer: Centennial Hall is mainly undergoing to the impact of pollutants emitted from the close coal power stations, whilst Casa Galleria Vichi is principally affected by pollutants from vehicular exhaust in front of the building.

Beiträge zur Chemie der schwersten Elemente in den Bereichen Elektrochemie und Chromatographie

Im Rahmen dieser Arbeit wurden Experimente auf verschiedenen Gebieten der chemischen Charakterisierung der schwersten Elemente durchgeführt. So wurden Vorarbeiten zur Elektrochemie der superschweren Elemente geleistet. Hier konnte gezeigt werden, dass sich Po aus verdünnten Säuren auf Metallelektroden spontan abscheiden lässt. Als wichtigste Reaktionsparameter wurden Temperatur, Konvektion und Viskosität des Elektrolyten identifiziert. Für die Elektrodeposition ist es von Bedeutung, reproduzierbar saubere Elektroden einzusetzen. Auch hierzu konnten Erkenntnisse gewonnen werden. Auf dem Gebiet der Charakterisierung von Nukliden wurde der Elektroneneinfang in Db-263 untersucht. Aus diesem Zerfall geht Rf-263 hervor, welches mit einer Halbwertszeit von 15min überwiegend durch Spontanspaltung zerfällt. Im Experiment wurde Rf-263 mittels Ionenaustauschchromatographie und nachfolgender Flüssig-Flüssig-Extraktion von Db und Aktiniden getrennt. Das erhaltene Präparat wurde auf Alpha-Zerfall und Spontanspaltung untersucht. Die Zahl der Rf-263 Zerfälle lässt auf einen Zerfallszweig durch Elektroneneinfang in Db-263 von 3% schließen. Ein Großteil der Arbeit beschäftigt sich mit der Bestimmung des Kd-Wertes von Sg am Anionenaustauscher Aminex A27 in 0.1M HNO3/5E-3M HF. Beim mit dem ALOHA-System durchgeführten Experiment wurde die Mehrsäulentechnik (MCT) erstmals für die wässrige Chemie von Sg genutzt. Aufgrund zahlreicher Probleme konnte letztlich kein Kd-Wert bestimmt werden. Stattdessen wurde das Experiment einer Fehleranalyse unterzogen. Hier zeigte sich eine Anfälligkeit der MCT auf natürliche Radionuklide. Weiterhin konnten Probleme bei ALOHA aufgedeckt werden, die eine Wiederholung des Experiments ausschlossen. In der Folge wurde ein alternativer Anionenaustauscher charakterisiert, sowie die Elektrolysebedingungen, als wichtiger Schritt der chemischen Aufarbeitung bei der MCT, genauer spezifiziert.

Synthetical engineering of supramolecular properties of large polycyclic aromatic hydrocarbons

An important property for devices is the charge-carrier mobility values for discotic organic materials like hexa-peri-hexabenzocoronenes. A close relation exists between the degree of their columnar self-arrangement of the molecules and their mobilities. Within this first step an induction of a higher order via hydrogen-bonding was considered, which mainly pointed towards the improvement of the intracolumnar stacking of the materials. For the analytics a broad range of methods was used including differential scanning calorimetry (DSC), wide-angle X-ray diffractometry (WAXS), solid-state NMR spectroscopy and scanning tunneling microscopy (STM). Indeed, a specific influence of the hydrogen-bonds could be identified, although in several cases by the cost of a severe reduction of solubility and processability. This effect was dampened by the addition of a long alkyl chain next to the hydrogen-bond exerting functional group, which resulted in an improved columnar arrangement by retention of processability. In contrast to the before mentioned example of inducing a higher intracolumnar order by hydrogen-bonding, the focus was also be set upon larger aromatic systems. The charge-carrier mobility is also in close relation to the size of the aromatic core and larger π-areas are expected to lead to improved mobilities. For photovoltaic applications a high extinction coefficient over a broad range of the spectrum is favorable, which can also be achieved by enlarging the aromatic core component. In addition the stronger π-interactions between the aromatic core components should yield an improved columnar stability and order. However the strengthening of the π-interactions between the aromatic core components led to a reduction of the solubility and the processability due to the stronger aggregation of the molecules. This required the introduction of efficiently solubilizing features in terms of long alkyl chains in the corona of the aromatic entity, in combination of a distortion of the aromatic core moiety by bulky tert-butyl groups. By this approach not only the processing and cleaning of the materials with standard laboratory techniques became possible, but moreover the first structure-rich UV/vis and a resolved 1H-NMR spectra for an aromatic system two times larger than hexa-peri-hexabenzocoronene were recorded. The bulk properties in an extruded fiber as well as on the surface showed a columnar self-assembly including a phase in which a homeotropic alignment on a substrate was observed, which turns the material into an interesting candidate for future applications in electronic devices.

Lifecycle analysis for surgery instruments at a hospital

Gli strumenti chirurgici sono importanti “devices” utilizzati come supporto indi-spensabile nella cura di pazienti negli ospedali. Essi sono caratterizzati da un intero ciclo di vita che inizia convenzionalmente nello “Store”, dove gli strumenti sterilizzati sono prelevati per essere utilizzati all’interno delle sale operatorie, e termina nuovamente nello “Store”, dove gli strumenti vengono immagazzinati per essere riutilizzati in un nuovo ciclo. Può accadere che le singole fasi del ciclo subiscano ritardi rispetto ai tempi previ-sti, non assicurando, pertanto, nelle sale operatorie, il corretto numero degli stru-menti secondo i tempi programmati. Il progetto che vado ad illustrare ha come obiettivo l’ottimizzazione del ciclo degli strumenti chirurgici all’interno di un nuovo ospedale, applicando i principi della Lean philosophy ed in particolare i metodi: “Poke Yoke, 5S e tracciabilità”. Per raggiungere tale scopo, il progetto è stato articolato come segue. In un primo momento si è osservato l’intero ciclo di vita degli strumenti nei due principali ospedali di Copenhagen (Hervel e Gentofte hospital). Ciò ha permesso di rilevare gli steps del ciclo, nonché di riscontrare sul campo i principali problemi relativi al ciclo stesso quali: bassa flessiblità, decentramento dei differenti reparti di cleaning e di store rispetto alle operation theatres ed un problema nel solleva-mento degli strumenti pesanti. Raccolte le dovute informazioni, si è passati alla fase sperimentale, in cui sono stati mappati due cicli di vita differenti, utilizzando tre strumenti di analisi: • Idef0 che consente di avere una visione gerarchica del ciclo; • Value stream Mapping che permette di evidenziare i principali sprechi del ciclo; • Simulator Tecnomatix che favorisce un punto di vista dinamico dell’analisi. Il primo ciclo mappato è stato creato con il solo scopo di mettere in risalto gli steps del ciclo e alcuni problemi rincontrati all’interno degli ospedali visitati. Il secondo ciclo, invece, è stato creato in ottica Lean al fine di risolvere alcuni tra i principali problemi riscontrati nei due ospedali e ottimizzare il primo ciclo. Si ricordi, infatti, che nel secondo ciclo le principali innovazioni introdotte sono state: l’utilizzo del Barcode e Rfid Tag per identificare e tracciare la posizione degli items, l’uso di un “Automatic and Retrievial Store” per minimizzare i tempi di inserimento e prelievo degli items e infine l’utilizzo di tre tipologie di carrello, per consentire un flessibile servizio di cura. Inoltre sono state proposte delle solu-zioni “Poke-Yoke” per risolvere alcuni problemi manuali degli ospedali. Per evidenziare il vantaggio del secondo ciclo di strumenti, è stato preso in consi-derazione il parametro “Lead time”e le due simulazioni, precedentemente create, sono state confrontate. Tale confronto ha evidenziato una radicale riduzione dei tempi (nonché dei costi associati) della nuova soluzione rispetto alla prima. Alla presente segue la trattazione in lingua inglese degli argomenti oggetto di ri-cerca. Buona lettura.

Valutazione dei criteri ambientali minimi del pan gpp per i servizi di pulizia e loro applicazione al piano di riduzione degli impatti ambientali del presidio ospedaliero di Conegliano

The subject of my thesis is to develop an assessment of minimum environmental criteria of the Plan National Action of Green Public Procurement for the cleaning service in the Conegliano’s hospital, used as case of study, through the Life Cycle Assessment methodology, to improve the hospital cleaning service.

OH- und HO 2-Radikale über dem tropischen Regenwald

Beständig werden Spurenstoffe in die Atmosphäre emittiert, die ihren Ursprung in biogenen oder anthropogenen Quellen haben. Daß es dennoch im allgemeinen nicht zu einer Anreicherung bis hin zu toxischen Konzentrationen kommt, liegt an dem Vermögen der Atmosphäre sich durch Oxidationsprozesse selbst zu reinigen. Eine wichtige Aufgabe kommt dabei dem Hydroxylradikal OH zu, welches tagsüber die Oxidationskapazität der Atmosphäre bestimmt. Hierbei spielen die tropischen Regionen mit einer der höchsten OH-Produktionsraten eine zentrale Rolle. Gleichzeitig sind die tropischen Regenwälder eine bedeutende globale Quelle für Kohlenwasserstoffe, die durch Reaktion mit OH-Radikalen dessen Konzentration und damit die Oxidationskapazität der Atmosphäre herabsetzen. Während der GABRIEL-Meßkampagne 2005 im äquatorialen Südamerika wurde der Einfluß der Regenwaldemissionen auf das HOx-Budget (HOx = OH+HO2) untersucht. Zu diesem Zweck wurde das Radikalmeßinstrument HORUS entwickelt. Im Rahmen dieser Arbeit wurden unterschiedliche Komponenten des Gerätes optimiert, der Meßaufbau ins Flugzeug integriert und Methoden zur Kalibrierung entwickelt. Bei der internationalen Vergleichskampagne HOxComp2005 zeigte HORUS seine Eignung zur Messung von troposphärischen OH- und HO2-Radikalen.rnrnDie durchgeführten HOx-Messungen während der GABRIEL-Meßkampagne sind die ersten ihrer Art, die über einem tropischen Regenwald stattgefunden haben. Im Gegensatz zu den Vorhersagen globaler Modelle wurden unerwartet hohe OH- und HO2-Konzentrationen in der planetaren Grenzschicht des tropischen Regenwalds beobachtet. Der Vergleich der berechneten OH-Produktions- und Verlustraten, die aus dem umfangreichen Datensatz von GABRIEL ermittelt wurden, zeigte, daß hierbei eine wichtige OH-Quelle unberücksichtigt blieb. Mit Hilfe des Boxmodells MECCA, in welchem die gemessenen Daten als Randbedingungen in die Simulationen eingingen, wurden die modellierten OH- und HO2- Konzentrationen im Gleichgewichtszustand den beobachteten Konzentrationen gegenübergestellt. Luftmassen der freien Troposphäre und der maritimen Grenzschicht zeigten eine gute Übereinstimmung zwischen Messung und Modell. Über dem tropischen Regenwald jedoch wurden die beobachteten HOx-Konzentrationen in der planetaren Grenzschicht durch das Modell, vor allem am Nachmittag, signifikant unterschätzt. Dabei lag die Diskrepanz zwischen den beobachteten und simulierten Konzentrationen bei einem mittleren Wert von OHobs/OHmod = 12.2 ± 3.5 und HO2obs/HO2mod = 4.1 ± 1.4. Die Abweichung zwischen Messung und Modell korrelieren hierbei mit der Isoprenkonzentration. Während für niedrige Isoprenmischungsverhältnisse, wie sie über dem Ozean oder in Höhen > 3 km vorherrschten, die Beobachtungen mit den Simulationen innerhalb eines Faktors 1.6±0.7 übereinstimmten, nahm die Unterschätzung durch das Modell für steigende Isoprenmischungsverhältnisse > 200 pptV über dem tropischen Regenwald zu.rnrnDer kondensierte chemische Mechanismus von MECCA wurde mit der ausführlichen Isoprenchemie des ”Master Chemical Mechanism“ überprüft, welches vergleichbare HOx-Konzentrationen lieferte. OH-Simulationen, durchgeführt mit der gemessenen HO2-Konzentration als zusätzliche Randbedingung, zeigten, daß die Konversion zwischen HO2 und OH innerhalb des Modells nicht ausreichend ist. Durch Vernachlässigung der gesamten Isoprenchemie konnte dagegen eine Übereinstimmung zwischen Modell und Messung erreicht werden. Eine OH-Quelle in der gleichen Größenordnung wie die OH-Senke durch Isopren, ist somit zur Beschreibung der beobachteten OH-Konzentration notwendig. Reaktionsmechanismen, die innerhalb der Isoprenchemie die gleiche Anzahl an OH-Radikalen erzeugen wie sie verbrauchen, könnten eine mögliche Ursache sein. Unterschiedliche zusätzliche Reaktionen wurden in die Isoprenabbaumechanismen des Modells implementiert, die zur Erhöhung der OH-Quellstärke führen sollten. Diese bewirkten eine Zunahme der simulierten HO2-Konzentrationen um einen maximalen Faktor von 5 für OH und 2 für HO2. Es wird eine OH-Zyklierungswahrscheinlichkeit r von bis zu 94% gefordert, wie sie für die GABRIEL-Messungen erreicht wurde. Die geringe OH-Zyklierungswahrscheinlichkeit von 38% des Modells zeigte, daß wichtige Zyklierungsvorgänge im chemischen Mechanismus bislang nicht berücksichtigt werden. Zusätzliche Zyklierungsreaktionen innerhalb des Isoprenmechanismus, die auch unter niedrigen NO-Konzentrationen zur Rückbildung von OHRadikalen führen, könnten eine Erklärung für die über dem Regenwald beobachteten hohen OH-Konzentration liefern.rn

Development of guidelines for microbiological control in microbrewery

Over the past 15 years the Italian brewing scene showed interesting changes, especially with regard to the creation of many breweries with an annual production of less than 10,000 hectoliters. The beers produced by microbreweries are very susceptible to attack by spoilage micro-organisms that cause the deterioration of beer quality characteristics. In addition, most of the microbreweries do not practice heat treatments of stabilization and do not carry out quality checks on the product. The high presence of beer spoilage bacteria is an economic problem for the brewing industry because it can damage the brand and it causes high costs of product retrieval. This thesis project was aimed to study the management of the production process in the Italian microbreweries within a production less than 10,000 hl. In particular, the annual production, type of plant, yeast management, process management, cleaning and sanitizing of a representative sample of microbreweries were investigated. Furthermore was made a collection of samples in order to identify, with simple methods, what are spoilage bacteria more present in the Italian craft beers. 21% of the beers analysed were positive at the presence of lactic acid bacteria. These analytical data show the importance of understanding what are the weak points of the production process that cause the development of spoilage bacteria. Finally, the thesis examined the actual production of two microbreweries in order to understand the process management that can promote the growth of spoilage bacteria in beer and production plant. The analysis of the data for the two case studies was helpful to understand what are the critical points where the microorganisms are most frequently in contact with the product. The hygiene practices are crucial to ensure the quality of the finished product, especially in the case of non-pasteurized beer.

Core-shell particles and their application for superhydrophobic surfaces

During the last years great effort has been devoted to the fabrication of superhydrophobic surfaces because of their self-cleaning properties. A water drop on a superhydrophobic surface rolls off even at inclinations of only a few degrees while taking up contaminants encountered on its way. rnSuperhydrophobic, self-cleaning coatings are desirable for convenient and cost-effective maintenance of a variety of surfaces. Ideally, such coatings should be easy to make and apply, mechanically resistant, and long-term stable. None of the existing methods have yet mastered the challenge of meeting all of these criteria.rnSuperhydrophobicity is associated with surface roughness. The lotus leave, with its dual scale roughness, is one of the most efficient examples of superhydrophobic surface. This thesis work proposes a novel technique to prepare superhydrophobic surfaces that introduces the two length scale roughness by growing silica particles (~100 nm in diameter) onto micrometer-sized polystyrene particles using the well-established Stöber synthesis. Mechanical resistance is conferred to the resulting “raspberries” by the synthesis of a thin silica shell on their surface. Besides of being easy to make and handle, these particles offer the possibility for improving suitability or technical applications: since they disperse in water, multi-layers can be prepared on substrates by simple drop casting even on surfaces with grooves and slots. The solution of the main problem – stabilizing the multilayer – also lies in the design of the particles: the shells – although mechanically stable – are porous enough to allow for leakage of polystyrene from the core. Under tetrahydrofuran vapor polystyrene bridges form between the particles that render the multilayer-film stable. rnMulti-layers are good candidate to design surfaces whose roughness is preserved after scratch. If the top-most layer is removed, the roughness can still be ensured by the underlying layer.rnAfter hydrophobization by chemical vapor deposition (CVD) of a semi-fluorinated silane, the surfaces are superhydrophobic with a tilting angle of a few degrees. rnrnrn

Supernova neutrinos in AMANDA and IceCube - Monte Carlo development and data analysis

Supernovae are among the most energetic events occurring in the universe and are so far the only verified extrasolar source of neutrinos. As the explosion mechanism is still not well understood, recording a burst of neutrinos from such a stellar explosion would be an important benchmark for particle physics as well as for the core collapse models. The neutrino telescope IceCube is located at the Geographic South Pole and monitors the antarctic glacier for Cherenkov photons. Even though it was conceived for the detection of high energy neutrinos, it is capable of identifying a burst of low energy neutrinos ejected from a supernova in the Milky Way by exploiting the low photomultiplier noise in the antarctic ice and extracting a collective rate increase. A signal Monte Carlo specifically developed for water Cherenkov telescopes is presented. With its help, we will investigate how well IceCube can distinguish between core collapse models and oscillation scenarios. In the second part, nine years of data taken with the IceCube precursor AMANDA will be analyzed. Intensive data cleaning methods will be presented along with a background simulation. From the result, an upper limit on the expected occurrence of supernovae within the Milky Way will be determined.

Tailoring properties and functionalities of TiO2 and Ag nanoparticles involved in surfaces engineering processes

The functionalization of substrates through the application of nanostructured coatings allows to create new materials, with enhanced properties. In this work, the development of self-cleaning and antibacterial textiles, through the application of TiO2 and Ag based nanostructured coatings was carried out. The production of TiO2 and Ag functionalized materials was achieved both by the classical dip-padding-curing method and by the innovative electrospinning process to obtain nanofibers doped with nano-TiO2 and nano-Ag. In order to optimize the production of functionalized textiles, the study focused on the comprehension of mechanisms involved in the photocatalytic and antibacterial processes and on the real applicability of the products. In particular, a deep investigation on the relationship between nanosol physicochemical characteristics, nanocoating properties and their performances was accomplished. Self-cleaning textiles with optimized properties were obtained by properly purifying and applying commercial TiO2 nanosol while the studies on the photocatalytic mechanism operating in self-cleaning application demonstrated the strong influence of hydrophilic properties and of interaction surface/radicals on final performance. Moreover, a study about the safety in handling of nano-TiO2 was carried out and risk remediation strategies, based on “safety by design” approach, were developed. In particular, the coating of TiO2 nanoparticles by a SiO2 shell was demonstrated to be the best risk remediation strategy in term of biological response and preserving of photoreactivity. The obtained results were confirmed determining the reactive oxygen species production by a multiple approach. Antibacterial textiles for biotechnological applications were also studied and Ag-coated cotton materials, with significant anti-bacterial properties, were produced. Finally, composite nanofibers were obtained merging biopolymer processing and sol-gel techniques. Indeed, electrospun nanofibers embedded with TiO2 and Ag NPs, starting from aqueous keratin based formulation were produced and the photocatalytic and antibacterial properties were assessed. The results confirmed the capability of electrospun keratin nanofibers matrix to preserve nanoparticle properties.

Diblock copolymer - nanocrystal hybrids for optoelectronic applications

Small, smaller, nano - it is a milestone in the development of new materials and technologies. Nanoscience is now present in our daily lives: in the car industry with self-cleaning surfaces, in medicine with cancer therapies, even our clothes and cosmetics utilize nanoparticles. The number and variety of applications has been growing fast in recent years, and the possibilities seem almost infinite. Nanoparticles made of inorganic materials have found applications in new electronic technologies, and organic nanomaterials have been added to resins to produce very strong but light weight materials.rnThis work deals with the combination of organic and inorganic materials for the fabrication of new, functional hybrid systems. For that purpose, block copolymers were made with a long, solubility-enhancing and semiconducting block, and a short anchor block. They were synthesized by either RAFT polymerization or Siegrist polycondensation. For the second block, an active ester was grafted on and subsequently reacted with the anchor molecules in a polymer analogue reaction. The resulting block copolymers had different properties; poly(para-phenylene vinylene) showed self-assembly in organic solvents, which resulted in gelling of the solution. The fibers from a diluted solution were visible through microscopy. When polymer chains were attached to TiO2 nanorods, the hybrids could be integrated into polymer fibers. A light-induced charge separation was demonstrated through KPFM. The polymer charged positively and the charge could travel along the fibers for several hundred nanometers. Polymers made via RAFT polymerization were based on poly(vinyltriphenylamine). Ruthenium chromophores which carried anchor groups were attached to the second block. These novel block copolymers were then attached to ZnO nanorods. A light-induced charge separation was also demonstrated in this system. The ability to disperse inorganic nanoparticles within the film is another advantage of these block copolymers. This was shown with the example of CdSe tetrapods. Poly(vinyltriphenylamine dimer) with disulfide anchor groups was attached to CdSe tetrapods. These four-armed nanoparticles are supposed to show very high charge transport. A polymer without anchor groups was also mixed with the tetrapods in order to investigate the influence of the anchor groups. It was shown that without them no good films were formed and the tetrapods aggregated heavily in the samples. Additionally, a large difference in the film qualities and the aggregation of the tetrapods was found in the sample of the polymer with anchor groups, dependent on the tetrapod arm length and the polymer loading. These systems are very interesting for hybrid solar cells. This work also illustrates similar systems with quantum dots. The influence of the energy level of the polymer on the hole transport from the polymer to the quantum dots, as well as on the efficiency of QLEDs was studied. For this purpose two different polymers were synthesized with different HOMO levels. It was clearly shown that the polymer with the adjusted lower HOMO level had a better hole injection to the quantum dots, which resulted in more efficient light emitting diodes.rnThese systems all have in common the fact that novel, and specially designed polymers, were attached to inorganic nanocrystals. All of these hybrid materials show fascinating properties, and are helpful in the research of new materials for optoelectronic applications.

Improvements in production and storage of HP-129 Xe

Seit seiner Entdeckung im Jahre 1978 wurden für hyperpolarisiertes (HP) 129Xe zahlreiche Anwendungen gefunden. Aufgrund seiner hohen Verstärkung von NMR-Signalen wird es dabei typischerweise für Tracer- und Oberflächenstudien verwendet. Im gasförmigen Zustand ist es ein interessantes, klinisches Kontrastmittel, welches für dynamische Lungen MRT genutzt oder auch in Blut oder lipophilen Flüssigkeiten gelöst werden kann. Weiterhin findet HP-Xe auch in der Grundlagenphysik in He-Xe Co-Magnetometern Verwendung, mit welchen z. B. das elektrische Dipolmoment von Xe bestimmt werden soll, oder es dient zur Überprüfung auf Lorentz-Invarianzen. Alle diese Anwendungen profitieren von einem hohen Polarisationsgrad (PXe), um hohe Signalstärken und lange Lagerzeiten zu erreichen. rnIn dieser Arbeit wurden zwei mobile Xe-Polarisatoren konstruiert: einer für Experimente in der Grundlagenphysik mit einer Produktionsrate von 400 mbar·l/h mit PXe ≈ 5%. Der zweite Xe-Polarisator wurde für medizinische Anwendungen entwickelt und soll 1 bar l/h mit PXe > 20% erzeugen. Der letztere wurde noch nicht getestet. Die Arbeitsbedingungen des Xe-Polarisators für Grundlagenphysik (Strömung des Gasgemischs, Temperatur, Druck und Konzentration von Xe) wurden variiert, um einen höchstmöglichen Polarisationsgrad zu erzielen. Die maximale Polarisation von 5,6 % wurde bei Verwendung eine Gasmischung von 1% Xe bei einem Durchfluss von 200 ml/min, einer Temperatur von 150°C und einem Gesamtdruck von 4 bar erreicht. rnWeiterhin muss HP-Xe auch effizient gelagert werden, um Polarisationsverluste zu minimieren. Das ist besonders für solche Anwendungen notwendig, welche an einem entfernten Standort durchgeführt werden sollen oder auch wenn lange Spinkohärenzeiten gefordert sind, z.B. bei He-Xe Co-Magnetometern. rnHierbei bestand bisher die größte Schwierigkeit darin, die Reproduzierbarkeit der gemessenen Lagerzeiten sicherzustellen. In dieser Arbeit konnte die Spin-Gitter-Relaxationszeit (T1) von HP-129Xe in unbeschichteten, Rb-freien, sphärischen Zellen aus Aluminiumsilikatglas (GE-180) signifikant verbessert werden. Die T1–Zeit wurde in einem selbstgebauten Niederfeld-NMR-System (2 mT) sowohl für reines HP-Xe als auch für HP-Xe in Mischungen mit N2, SF6 und CO2 bestimmt. Bei diesen Experimenten wurde die maximale Relaxationszeit für reines Xe (85% 129 Xe) bei (4,6 ± 0,1) h festgestellt. Dabei lagen die typischen Wand-Relaxationszeiten bei ca. 18 h für Glaszellen mit einem Durchmesser von 10 cm. Des Weiteren wurde herausgefunden, dass CO2 eine unerwartet hohe Effizienz bei der Verkürzung der Lebensdauer der Xe-Xe Moleküle zeigte und somit zu einer deutlichen Verlängerung der gesamten T1-Zeit genutzt werden kann. rnIm Verlauf vieler Experimente wurde durch wiederholte Messungen mit der gleichen Zelle, ein "Alterungsprozess“ bei der Wandrelaxation identifiziert und untersucht. Dieser Effekt könnte leicht rückgängig gemacht werden, indem die anfängliche Reinigungsprozedur wiederholt wurde. Auf diese Weise kann eine konstante Wandrelaxation sichergestellt werden, durch die sehr reproduzierbare T1-Messungen möglich werden. rnSchließlich wurde die maximale Relaxationszeit für HP-Xe mit natürlicher Häufigkeit in Mischungen mit SF6 bestimmt. Überraschenderweise war dieser Wert um ca. 75% niedriger als der Wert für Xenon, das zu 85% mit 129Xe angereichert war. Dieser Effekt wurde durch drei unabhängige Experimente bestätigt, da er nicht von der bestehenden Theorie der Xe-Relaxation ableitbar ist. rnDie Polarisation von HP-Xe, PXe, wird normalerweise durch den Vergleich der NMR-Signale des HP-Xe mit einer thermischen polarisierten Probe (z. B. 1H2O oder Xe) bestimmt. Dabei beinhaltet der Vergleich unterschiedlicher Messungen an verschiedenen Proben (unterschiedlicher Druck, Signalintensität und Messverfahren) viele experimentelle Unsicherheiten, welche sich oft nicht leicht bestimmen lassen. Eine einfache, genaue und kostengünstige Methode zur Bestimmung von PXe durch eine direkte Messung der makroskopischen Magnetisierung in einem statischen Magnetfeld vermeidet alle diese Unsicherheiten. Dieses Verfahren kann Polarisationen von > 2 % mit einer Genauigkeit von maximal 10% fast ohne Polarisationsverlust bestimmen. Zusätzlich kann diese Methode ohne weitere Änderungen auch für Bestimmungen des Polarisationsgrades anderer HP-Gase verwendet werden.rn

Progettazione ed implementazione di un data warehouse di supporto alla profilazione dei consumi energetici domestici

Sviluppo e analisi di un dataset campione, composto da circa 3 mln di entry ed estratto da un data warehouse di informazioni riguardanti il consumo energetico di diverse smart home.

Hand and ultrasonic instrumentation for orthograde root canal treatment of permanent teeth

Root canal treatment is a frequently performed dental procedure and is carried out on teeth in which irreversible pulpitis has led to necrosis of the dental pulp. Removal of the necrotic tissue remnants and cleaning and shaping of the root canal are important phases of root canal treatment. Treatment options include the use of hand and rotary instruments and methods using ultrasonic or sonic equipment. OBJECTIVES: The objectives of this systematic review of randomized controlled trials were to determine the relative clinical effectiveness of hand instrumentation versus ultrasonic instrumentation alone or in conjunction with hand instrumentation for orthograde root canal treatment of permanent teeth. MATERIAL AND METHODS: The search strategy retrieved 226 references from the Cochrane Oral Health Group Trials Register (7), the Cochrane Central Register of Controlled Trials (CENTRAL) (12), MEDLINE (192), EMBASE (8) and LILACS (7). No language restriction was applied. The last electronic search was conducted on December 13th, 2007. Screening of eligible studies was conducted in duplicate and independently. RESULTS: Results were to be expressed as fixed-effect or random-effects models using mean differences for continuous outcomes and risk ratios for dichotomous outcomes with 95% confidence intervals. Heterogeneity was to be investigated including both clinical and methodological factors. No eligible randomized controlled trials were identified. CONCLUSIONS: This review illustrates the current lack of published or ongoing randomized controlled trials and the unavailability of high-level evidence based on clinically relevant outcomes referring to the effectiveness of ultrasonic instrumentation used alone or as an adjunct to hand instrumentation for orthograde root canal treatment. In the absence of reliable research-based evidence, clinicians should base their decisions on clinical experience, individual circumstances and in conjunction with patients' preferences where appropriate. Future randomized controlled trials might focus more closely on evaluating the effectiveness of combinations of these interventions with an emphasis on not only clinically relevant, but also patient-centered outcomes.

Metallic copper as an antimicrobial surface

Bacteria, yeasts, and viruses are rapidly killed on metallic copper surfaces, and the term "contact killing" has been coined for this process. While the phenomenon was already known in ancient times, it is currently receiving renewed attention. This is due to the potential use of copper as an antibacterial material in health care settings. Contact killing was observed to take place at a rate of at least 7 to 8 logs per hour, and no live microorganisms were generally recovered from copper surfaces after prolonged incubation. The antimicrobial activity of copper and copper alloys is now well established, and copper has recently been registered at the U.S. Environmental Protection Agency as the first solid antimicrobial material. In several clinical studies, copper has been evaluated for use on touch surfaces, such as door handles, bathroom fixtures, or bed rails, in attempts to curb nosocomial infections. In connection to these new applications of copper, it is important to understand the mechanism of contact killing since it may bear on central issues, such as the possibility of the emergence and spread of resistant organisms, cleaning procedures, and questions of material and object engineering. Recent work has shed light on mechanistic aspects of contact killing. These findings will be reviewed here and juxtaposed with the toxicity mechanisms of ionic copper. The merit of copper as a hygienic material in hospitals and related settings will also be discussed.